Engine driven vehicles such as ATVs (All Terrain Vehicles, so-called buggies), tractors, or recreation vehicles that are engine driven vehicles intended mainly for driving on rough ground have been incorporating a generator driven by an engine for driving the vehicle to supply a commercial AC output of AC 100 V, AC 200 V (50 Hz or 60 Hz), or the like to a load while the vehicle is stopped, in order to allow electric tools or home appliances to be used outdoors. Such an engine driven vehicle is, for example, disclosed in Japanese Patent Laid-Open No. 2004-92634.
In such an engine driven vehicle, a gear position sensor that detects a gear position of a power transmission device is provided, and only when the gear position sensor detects that the gear position is in a position for cutting power transmission, control of a rotational speed in a power generation mode is performed, in order to prevent the vehicle from starting when the generator is operated.
As described above, if the control of the rotational speed in the power generation mode is performed only when the gear position sensor detects that the gear position is in the position for cutting power transmission, the vehicle can be prevented from starting during an operation in the power generation mode. In the engine driven vehicle thus comprised, however, if a driver inadvertently operates a throttle valve to an acceleration side during the operation in the power generation mode, the rotational speed of the engine increases to cause an excessive output of the generator, which may break a circuit connected to an output side of the generator or a load of the generator.
Further, even in the case where the control of the rotational speed in the power generation mode is performed only when the gear position sensor detects that the gear position is in the position for cutting power transmission, if the gear position sensor or a gearbox is broken, the power generation mode may be selected when false detection is made that the power transmission device is in a state for cutting power transmission though the power transmission device is actually in a state for transmitting power. In this case, if the power transmission device includes a centrifugal clutch, the rotational speed of the engine is increased when the power transmission device is in the state for transmitting power to drive wheels at a start of the operation of the generator, and thus the rotational speed of the engine may exceed a clutch-in speed of the centrifugal clutch to cause the vehicle to start.
In order to avoid such problems, it is preferable that an allowable rotational speed of the engine in the operation in the power generation mode is previously determined, and the rotational speed of the engine does not exceed the allowable rotational speed when the throttle valve is operated during the operation in the power generation mode.